A $10.6 million expansion is under way at the city of Post Falls wastewater treatment plant that will increase its capacity and help reduce odors, says Terry Werner, the city's public works director.

The upgrade will enable the plant to treat 5 million gallons of wastewater a day, an increase of 32 percent over its current capacity of 3.8 million gallons a day, Werner says.

The plant, located at 2002 W. Seltice Way, just north of Interstate 90 and about midway between the freeway's Pleasant View Road and Spokane Street interchanges, treats wastewater for the North Idaho cities of Post Falls and Rathdrum.

Boise-based J-U-B Engineers Inc. designed the expansion project and will manage construction of it through its Coeur d'Alene office. Record Steel & Construction Inc., of Meridian, Idaho, is the contractor.

Werner says the capacity upgrade should be sufficient to meet added demand for five to 10 years, depending on the rate of growth in the area.

The project will include new concrete clarifier and oxidation basins, which are used to settle out biosolids and optimize growth of bacteria and organisms that aid in the treatment process, he says. The project also should address complaints of odor that sometimes wafts over the freeway, he says.

"Part of the project is to put in odor-control measures in the head works, where solids are removed from the digester," Werner says. The plant's treated wastewater is piped to the Spokane River and the biosolids are shipped to a commercial-compost maker in Missoula, Mont., he adds.

Future technological upgrades likely will be needed at the plant to meet anticipated stringent federal water quality standards, which will require reduced levels of phosphorus, Werner says. The city also is looking at potential land-application measures to dispose of treated wastewater, he adds.